DESCRIPTION: The objective of this proposal is to develop a small molecule-based treatment strategy for MS. The principal investigator will employ surface mimetics of CD4 which correspond to the CDR3-like external domain of the murine CD4 molecule (the D1 domain) which contains a hydrophilic sequence (ELENRKEE) and a hydrophobic sequence that presumably partitions itself away from the hydrophilic domain. Dr. Jameson has prepared a PGP-containing analog of the CDR3 sequence with a cysteine residue at each end which form a disulfide bond, and thus provide conformational constraint. This PGP-analog has been shown to specifically inhibit CD4-dependent responses, including MLR, and EAE. An advantage over the use of anti-CD4 antibody is that this PGP-analog primarily inhibits activated TH1 cells, thus leaving naive CD4 cell function relatively intact. Drawbacks encountered to date have included low potency of the peptide mimetics and batch-to-batch inconsistencies in the biological activity of different preparations of these analogs. NMR data suggest that the disulfide-bonded PGP-analog presents a wide range of conformations but that individual molecules are effectively locked into a given conformation. This implies that there is little control over which populations dominate, and consequently, little control over which batches will be biologically active. Dr. Jameson believes he can circumvent this problem by utilizing a peptoid template. The peptoid has an N-substituted glycine backbone which may be more amenable to manipulation, thus permitting flexible structure which will maintain the same spacing of the amino acid sidechains but without the "trapped conformations" that adversely affect the biological activity of the peptide-based analogs. The principal investigator will construct a series of peptoid mimetics of the CDR3 sequence from the murine CD4 molecule and determine the structure-activity relationship (SAR) to ascertain which peptoids have biological activity in MLR and EAE models. The ultimate objective is to apply the information obtained to therapy in multiple sclerosis.